There has been conventionally disclosed a device such that in a heat transfer tube arranged in a zigzag pattern by a bent part formed in a path of flue gas, because wear of a bent part near a furnace wall where a drift occurs is large, a baffle plate is placed on the furnace wall between adjacent bent parts, so that a drift is prevented (for example, see Patent Literature 1).
Further, a device for preventing wear of a looped tube in a rear heat transfer unit of a coal combustion boiler has been disclosed, where the rear heat transfer unit is connected via a sub-sidewall to a rear side of a furnace, and a reheater and a superheater that are constituted by a plurality of looped tubes are placed in the rear heat transfer unit, an erosion baffle that has a predetermined width in a substantially horizontal direction to extend toward a flow path is mounted on a heat transfer tube wall that constitutes the rear heat transfer unit above bent ends of looped tubes of the reheater and the superheater, and holes for passing coal ash are formed on the entire surface of the erosion baffle (for example, see Patent Literature 2).
Further, there has been disclosed a device in which a drift preventing plate is provided at a position on a sidewall of a boiler above heat exchanger tubes (for example, see Patent Literature 3).
Further, there has been disclosed a horizontal-type heat exchanger for a coal combustion boiler. In this heat exchanger, to prevent wear and damage of a heat transfer tube due to coal ash, a horizontal element is constituted by bare tubes for the second tier from the top and spiral fin tubes for the third and subsequent tiers, and a drift preventing plate is provided because a large amount of gas flows into a space between an end of the horizontal element and a sidewall tube and then tubes near the space are damaged (for example, see Patent Literature 4).
Further, there has been disclosed an exhaust-heat recovery unit that recovers heat from flue gas in a gas turbine. The exhaust-heat recovery unit includes a duct for which four surfaces are respectively constituted by front, rear, and side duct casings and in which flue gas passes, and a finned heat transfer tube group constituted by a plurality of finned heat transfer tubes that are provided in the duct so as to be perpendicular to a flow direction of the flue gas and whose axis longitudinal direction is in parallel with the side duct casing. In this exhaust-heat recovery unit, baffles that are fixed to inner surfaces of the side duct casings on an upstream side and a downstream side of flue gas in the finned heat transfer tube group so as to cover ends of the finned heat transfer tube group along the tube axis longitudinal direction are provided (for example, see Patent Literature 5).
As described above, various types of regulating plates (a baffle plate, an erosion baffle, a drift preventing plate, and a baffle) have been conventionally proposed to make a gas flow in a heat exchanger (a heat transfer tube, a repeater, a heater, a heat exchanger tube a heat transfer tube, or an exhaust-heat recovery unit) uniform.
However, according to the devices described in Patent Literatures 1 to 5, regulating plates are provided only near a heat exchanger and thus sufficient regulation (reduction in drift) cannot be achieved.
Citation List
Patent Literatures
Patent Literature 1: Japanese Utility Model Laid-open Publication No. S60-128107 (Japanese Utility Model Application No. S59-12671)
Patent Literature 2: Japanese Patent Application Laid-open No. H08-110007
Patent Literature 3: Japanese Patent Application Laid-open No. H11-72202
Patent Literature 4: Japanese Patent Application Laid-open No. H11-118101
Patent Literature 5: Japanese Patent Application Laid-open No. H9-137906